The main cause of the abnormal growth of cancer cells is the dysfunction of the signal transduction system for cell growth factors. For example, various types of tumor cells have been found to secrete tumor growth factor alpha (TGF-.alpha.) which enhances the autoproliferation of the tumor cells. An agent which can selectively inhibit the action of TGF-.alpha. can thus be expected to be useful as an anticancer agent.
Erbstatin and other agents of this sort are known. However, they are not sufficiently potent and, moreover, are not clinically useful because they lose their effects in blood.
Accordingly, an object of the present invention is to provide a novel substance which inhibits the action of tumor growth factors and inhibits the growth of tumor cells. Another object of the present invention is to provide an antitumor agent comprising the substance.
The inventors of the present invention screened various inhibitors using Epidermal growth factor (EGF), a cell growth factor similar to TGF-.alpha.. As a result, the inventors found that a novel substance, Reveromycin A, has potent inhibitory activity against EGF and inhibits the growth of various kinds of tumor cells. The present invention was achieved on the basis of this findings.
Furthermore, the inventors also found that Reveromycin A has antimicrobial activity against fungi and that a pharmaceutical composition comprising this substance is useful as an antifungal agent for achieving the present invention.